1. Field of the Invention
The present invention relates to an ultrasonic liquid-crystal display by means of using a dispersive interdigital transducer on a piezoelectric substrate formed on a first surface-part of a nonpiezoelectric bottom-plate, a sandwich formed on a second surface-part of the nonpiezoelectric bottom-plate and composed of a liquid crystal between first- and second conducting electrodes, and a nonpiezoelectric upper-plate on the sandwich.
2. Description of the Prior Art
In recent years, liquid-crystal displays act important parts on computers, portable communication devices, and so on. The thin-film transistor (TFT)-type liquid-crystal display, which is a popular one of conventional liquid-crystal displays, is good in quality. However, it is unavoidable that an electric power consumption to the backlight is 70xcx9c80% of all the electric power consumption to the display. Using reflective-type displays in place of nonreflective-type displays such as the TFT-type display cause a decrease in electric power. The reflective-type displays, for example, polymer dispersed display and guest-host mode display have problems on response time, accuracy and clearness, durability and manufacturing, electric power consumption, range of vision, inferiority in liquid crystal, and device size. On the other side, dynamic scattering mode display, which is the initial type, is not adequate for practical use at present.
An object of the present invention is to provide an ultrasonic liquid-crystal display with high accuracy and clearness.
Another object of the present invention is to provide an ultrasonic liquid-crystal display excellent in durability and manufacturing.
Another object of the present invention is to provide an ultrasonic liquid-crystal display operating with a quick response time.
Another object of the present invention is to provide an ultrasonic liquid-crystal display operating under low electric power consumption with low voltage.
Another object of the present invention is to provide an ultrasonic liquid-crystal display excellent in the range of vision.
Another object of the present invention is to provide an ultrasonic liquid-crystal display without the inferiority in liquid crystal.
Another object of the present invention is to provide an ultrasonic liquid-crystal display without a backlight behind the display.
Another object of the present invention is to provide an ultrasonic liquid-crystal display without polarizers.
A still other object of the present invention is to provide an ultrasonic liquid-crystal display having a small size and a simple structure which is very light in weight.
According to one aspect of the present invention there is provided an ultrasonic liquid-crystal display comprising a nonpiezoelectric bottom-plate, a piezoelectric substrate on a first surface-part of an upper end-surface of the nonpiezoelectric bottom-plate, at least one dispersive interdigital transducer on the piezoelectric substrate, a nonpiezoelectric upper-plate, first- and second conducting electrodes, and a liquid crystal between the first- and second conducting electrodes. The nonpiezoelectric bottom-plate and a nonpiezoelectric upper-plate have a transparency, respectively. The second surface-part of the upper end-surface of the nonpiezoelectric bottom-plate is covered with the first conducting electrode. The lower end-surface of the nonpiezoelectric upper-plate is covered with the second conducting electrode.
When a first electric signal is applied to the dispersive interdigital transducer, a frequency modulated chirp surface acoustic wave (an FM chirp-SAW) is excited in the piezoelectric substrate. The FM chirp-SAW is transmitted to the liquid crystal through the upper end-surface of the nonpiezoelectric bottom-plate, and causes the liquid crystal cloudy. In case of the liquid crystal being cloudy, if a second electric signal is applied between the first- and second conducting electrodes, that is, electric field is applied to the liquid crystal, the liquid crystal becomes cloudless.
According to another aspect of the present invention there is provided a piezoelectric substrate made of a piezoelectric ceramic thin plate, the polarization axis thereof being parallel to the thickness direction thereof.
According to another aspect of the present invention there is provided a piezoelectric substrate having a thickness smaller than the smallest interdigital periodicity of the dispersive interdigital transducer.
According to another aspect of the present invention there are provided a nonpiezoelectric bottom-plate and a nonpiezoelectric upper-plate, which have a thickness larger than two times the largest interdigital periodicity of the dispersive interdigital transducer, respectively.
According to another aspect of the present invention there is provided an ultrasonic liquid-crystal display, wherein the phase velocity of the FM chirp-SAW on the nonpiezoelectric bottom-plate alone is higher than that in the piezoelectric substrate alone.
According to another aspect of the present invention there is provided a liquid crystal made of a nematic liquid crystal.
According to another aspect of the present invention there is provided a liquid crystal, which is homogeneously oriented before receiving the FM chirp-SAW.
According to another aspect of the present invention there are provided first- and second conducting electrodes consisting of transparent electrodes made of indium-tin oxide.
According to another aspect of the present invention there are provided first- and second conducting electrodes comprising a group of slender subelectrodes, which form a stripe pattern, respectively. A stripe direction of the first conducting electrode and that of the second conducting electrode are vertical from each other. When the second electric signal is applied between at least one of the subelectrodes of the first conducting electrode and that of the second conducting electrode, electric field is applied to at least one crossing zone, in the liquid crystal, between the subelectrodes of the first- and second conducting electrodes. Thus, the crossing zone becomes cloudless.
According to another aspect of the present invention there are provided another piezoelectric substrate on a third surface-part of the upper end-surface of the nonpiezoelectric bottom-plate, and at least one input interdigital transducer thereon. The input interdigital transducer has the reverse electrode-finger pattern to the dispersive interdigital transducer. When a third electric signal is applied to the input interdigital transducer at the same time that the first electric signal is applied to the dispersive interdigital transducer, another FM chirp-SAW is excited in the piezoelectric substrate on the third surface-part of the upper end-surface of the nonpiezoelectric bottom-plate. The FM chirp-SAW is transmitted to the liquid crystal, and causes the liquid crystal further cloudy.
According to another aspect of the present invention there are provided another piezoelectric substrate on a third surface-part of the upper end-surface of the nonpiezoelectric bottom-plate, at least one output interdigital transducer thereon, and an amplifier connected between the dispersive interdigital transducer and the output interdigital transducer. The output interdigital transducer has the same electrode-finger pattern as the dispersive interdigital transducer.
According to another aspect of the present invention there is provided a light source under the nonpiezoelectric bottom-plate.
According to another aspect of the present invention there is provided a mirror under the nonpiezoelectric bottom-plate.
According to another aspect of the present invention there are provided first- and second polarizers and a color filter.
According to other aspect of the present invention there is provided an ultrasonic liquid-crystal display comprising at least two ultrasonic subdisplays forming a stacked body. Each of the ultrasonic subdisplays consists of a nonpiezoelectric bottom-plate having a transparency, a piezoelectric substrate on a first surface-part of an upper end-surface of the nonpiezoelectric bottom-plate, at least one dispersive interdigital transducer on the piezoelectric substrate, a nonpiezoelectric upper-plate, first- and second conducting electrodes, and a liquid crystal between the first- and second conducting electrodes. A second surface-part of the upper end-surface of the nonpiezoelectric bottom-plate is covered with the first conducting electrode. A lower end-surface of the nonpiezoelectric upper-plate is covered with the second conducting electrode.
According to a further aspect of the present invention there is provided an ultrasonic liquid-crystal display comprising a piezoelectric transparent substrate, at least one dispersive interdigital transducer on a first surface-part of an upper end-surface of the piezoelectric transparent substrate, a transparent nonpiezoelectric plate, first- and second conducting electrodes, and a liquid crystal between the first- and second conducting electrodes. A second surface-part of the upper end-surface of the piezoelectric transparent substrate is covered with the first conducting electrode. A lower end-surface of the transparent nonpiezoelectric plate is covered with the second conducting electrode.
When a first electric signal is applied to the dispersive interdigital transducer, an FM chirp-SAW is excited on the first surface-part of the upper end-surface of the piezoelectric transparent substrate. The FM chirp-SAW is transmitted to the liquid crystal through the second surface-part of the upper end-surface of the piezoelectric transparent substrate, and causes the liquid crystal cloudy. In case of the liquid crystal being cloudy, if a second electric signal is applied between the first- and second conducting electrodes, that is, electric field is applied to the liquid crystal, the liquid crystal becomes cloudless.